The present invention relates to pulse-forming networks in general, and in particular to a circuit for providing additional current during pulse transitions in order to achieve fast output risetimes and falltimes.
Pulse generators are used in a variety of circuit testing applications, and are therefore available as electronic test and measurement instruments which produce pulses having specified parameters that can be adjusted independently of one another. These parameters include pulse amplitude, pulse width, repetition rate, risetime and falltime. The active components (e.g., diodes and transistors) of the output stages of such pulses generators typically exhibit large capacitances which determine the slew rate of pulse transitions. To achieve fast output risetimes and falltimes of pulses, which may typically be in the sub-nano-second to a few nanoseconds range, the output stages have had to stand large amounts of current in order to drive these capacitances. While providing a solution to overcome the limiting effects of inherent capacitance on the risetimes and falltimes of output pulses, standing a large amount of current results in a large amount of wasted power which is manifested as heat.